PROGRESS IN HIGH-ENERGY DENSITY DISORDERED ROCKSALT CATHODE MATERIALS

Transcription

1 PROGRESS IN HIGH-ENERGY DENSITY DISORDERED ROCKSALT CATHODE MATERIALS G. Ceder Lawrence Berkeley National Laboratory UC Berkeley Nature Conference Shenzhen, Jan

2 This presentation is available at Percolation in cation-disordered structures J. Lee, et al., Science, 343 (6170), (2014) A. Urban, et al. Adv. Energy Mater. 4 (2014) J. Lee, G. Ceder et al, Energy Env Sc. 8, 3255 (2015) A Urban, A Abdellahi, S Dacek, N Artrith, G Ceder, Phys. Rev. Lett. 119, , DOI: /PhysRevLett (2017) Fluorination J. Lee, G. Ceder et al, Nat. Comm, 8, art number 981 (2017) W. Richards, S. Dacek, D. Kitchaev, G. Ceder, Fluorination of Lithium-Excess Transition Metal Oxide Cathode Materials, Advanced Energy Materials, DOI: /aenm (2017). Oxygen redox activity and covalency D.-H. Seo, J. Lee, A. Urban, R. Malik, S. Kang, G. Ceder, Nature Chem., Advance Online Publication (2016). MK. Aydinol, AF. Kohan, G. Ceder, K. Cho, J. Joannopoulos, Phys. Rev. B, 56, (1997) Electronic Structure effects on Transition Metal Migration J. Reed and G. Ceder, Chemical Reviews, 104 (10), (2004). Cobalt resources and projections E. A. Olivetti, G. Ceder, GG. Gaustad, X. Fu, \Joule 1, , 2017, DOI: j.joule (2017)

3 Why is cathode chemistry limited? Layered LiMO2 Most Li-ion cathodes are layered materials in the LCO, NCA, NMC-class materials LCO: LiCoO 2 NCA: Li(Ni 0.8 Co 0.15 Al 0.05 O 2 NCM: Li(Ni 1/3 Co 1/3 Mn 1/3 O 2 LRNCM: Li(Li,Ni, Co, Mn)O 2 Co, Ni and Mn 4+ are resistant against migration Co 3+ Co 4+ Mn 4+ Ni 2+ Ni 3+ Ni 4+

4 Fundamental limita4ons to NMC-like cathodes DEMAND: By 2026 demand for Li-ion energy storage is likely to be in the range GWh/year, with 1000 GWh/year if electrification of vehicles intensifies. May require between 140,000 to 300,000 tonnes of Cobalt. E. A. Olivetti, G. Ceder, GG. Gaustad, X. Fu, \Joule 1, , 2017, DOI: j.joule (2017)

5 Fundamental limita4ons to NMC-like cathodes DEMAND: By 2026 demand for Li-ion energy storage is likely to be in the range GWh/year, with 1000 GWh/year if electrification of vehicles intensifies. May require between 140,000 to 300,000 tonnes of Cobalt $ $30 $24 $33 At $100/kg-Co NMC622 = $20 Co alone Jan 2015 Jan 2016 Jan 2017 Jan 2018 SAFETY: NMC s all require oxidation of a large amount of Ni to Ni4+, which in unstable. Need to break this chain between capacity and safety problems

6 Why these elements? Mobility of TM is controlled by its electronic structure Tetrahedral site is the activated state as TM migrates into Li layer Tetrahedral vs octahedral site preference is controlled by number of d-electrons e g t 2g octahedral Ligand field gap Filling these orbitals favors octahedral occupation Reed et al. Electrochem. Solid State Le6. (2001)

7 Electronic structure determines Tet/Oct preference Ti 4+ V 4+ Cr 4+ Mn 4+ Fe 4+ Co 4+ Ni 4+ Ti 3+ V 3+ Cr 3+ Mn 3+ Fe 3+ Co 3+ Ni 3+ Mn 2+ Ni 2+ Marginal Reed and GC Chemical Reviews, 104 (10), (2004). Reed et al. Electrochem. Solid State Le6. (2001)

8 Why do we need cathodes to be layered? Or can they be disordered as well?

9 Li diffusion mechanism in rocksalts Gate ions Li hopping from oct to oct site through tetrahedral site Tetrahedral site is approximately the activated state

10 In layered oxides one gate-ion is a Transition Metal (TM) Increase slab spacing allows the TM to relax further away from the Li in the activated state Activated state [K Kang and G Ceder Phys. Rev. B 74 (2006) ] Every 0.1 Å in slab space reduction reduces D Li by more than a factor of 10 A. Van der Ven, G. Ceder, Electrochemical and Solid State Letters 3, (2000)

11 Disorder reduces slab distance Disordered Disordering leads to smaller tetrahedral height, which chokes the 1-TM barrier Layered A. Urban, et al. Adv. Energy Mater. 4 (2014)

12 The environments around the activated state 1-TM 0-TM 2-TM 3-TM 4-TM

13 NEB calculations show that 0-TM channels are much less sensitive to lattice parameter 0-TM channels will be active in disordered rocksalts! J. Lee, et al., Science, 343 (6170), (2014)

14 Disordered materials function by diffusion through different channel 0-TM We can now use ANY transition metal cation, not just Co, Ni and Mn 4+ 1-TM 1-TM channel cannot operate when disorder occurs By adding Li excess > 10% the material achieves an additional Li diffusion mechanism which is insensitive to disorder

15 Disordered rocksalt cathodes continue to function even with extreme cation disorder. Concept discovered in 2014 with Li Mo Cr 0.3 O 2 Before cycling 1 cycle 10 cycles J. Lee, G. Ceder et al., Science, 343 (6170), (2014)

16 Now lots of Li-excess rocksalts: LEX-RS Li Mo Cr 0.3 O 2 Li 1.25 Nb 0.25 Mn 0.5 O Wh/kg, 3350 Wh/l Density = 4.7 J. Lee, et al. Science, 343 (6170), (2014) Li 1.2 Ni 0.32 Ti 0.35 Mo O 2 Wang and Ceder, Electrochem Comm. V60 P Yabuuchi and Komaba, PNAS 2015 Li 2 VO 2 F J. Lee and G. Ceder, Energy Environ. Sci., 8 (11), (2015). Chen R.,Fichtner Adv. Energy Mater., 5:

17 More Li-excess disordered materials Li (1+x) Ti 2x Fe (1 3x) O 2 Li 1.2 Mn 0.4 Ti 0.4 O 2 ~220 mah/g Kitajou et al., Electrochemistry (2016) Glazier, SL et al. Chem Mat DOI: / 2015, 27,

18 Which compositions creates disordered rocksalts? Layered Cation Disordered Regular octahedra. Layering due to size difference between TM and Li Which ions can easily accommodate distortions?? Distorted octahedra. Related to the electronic structure

19 Distortions can be Described by Normal Modes Octahedral distortions can be decomposed into normal modes STRUCTURE = Stretching (Jahn-Teller) Bending Twisting TM Displacement TM dependent TM d Orbitals ELECTRONIC STRUCTURE e * g t 2g Shift of each of these orbitals is simply related to amplitude of each deformation mode

20 Each Mode has a Different Effect on Energy Levels A d 0 ion can best accommodate general distortions e.g. Co 3+ e.g. Nb 5+, Ti 4+ d 0 is great to accommodate disorder A Urban, A Abdellahi, S Dacek, N Artrith, G Ceder, Phys. Rev. Lett. 119, , DOI: /PhysRevLett (2017)

21 All known Cation-Disordered LiMO 2 Compositions Contain d 0 Transition-Metal Species Composition TM Cations Li 1+x V 2 O 5 V 3+, V 5+ LiM 0.5 Ti 0.5 O 2 (M = Fe, Ni) M 2+, Ti 4+ Li Mo Cr 0.3 O 2 Mo 5+, Cr 3+ Li 1.3 Nb 0.3+x M 0.4-x O 2 (M = Mn, Fe, Co, Ni) Nb 5+, M 3+ Li 1.6-4x Mo 0.4-x Ni 5x O 2 Mo 6+, Ni 2+ Li 1.3 Nb 0.3 V 0.4 O 2 Nb 5+, V 3+ LiCo 0.5 Zr 0.5 O 2 Co 2+, Zr 4+ Disorders when Mo 5+ is oxidized to d 0 Mo 6+ C. Delmas, S. Brèthes, and M. Ménétrier, J. Power Sources 34, 113 (1991). L. Zhang, H. Noguchi, D. Li, T. Muta, X. Wang, M. Yoshio, and I. Taniguchi, J. Power Sources 185, (2008). H. Shigemura, M. Tabuchi, H. Sakaebe, H. Kobayashi, and H. Kageyama, J. Electrochem. Soc. 150, A638 (2003). J. Lee, A. Urban, X. Li, D. Su, G. Hautier, and G. Ceder, Science 343, 519 (2014). R. Wang, X. Li, L. Liu, J. Lee, D.-H. Seo, S.-H. Bo, A. Urban, and G. Ceder, Electrochem. Commun. 60, (2015). N. Yabuuchi, S. Komaba et al., Proc. Natl. Acad. Sci. USA 112, (2015). N. Yabuuchi, Y. Tahara, S. Komaba, S. Kitada, and Y. Kajiya, Chem. Mater. 28, 416 (2016). N. Yabuuchi, M. Takeuchi, S. Komaba, S. Ichikawa, T. Ozaki, and T. Inamasu, Chem. Commun. 52, 2051 (2016). A. Urban, I. Matts, A. Abdellahi, and G. Ceder, Adv. Energy Mater. 6, (2016).

22 Li(Ni 0.5 Ti 0.5 )O 2 is disordered d 0 Ti 4+ absorbs distortions à Ni 2+ sites close to ideal Li(Ni 0.5 Mn 0.5 )O 2 is ordered d 8 Ni 2+ distorts strongly à Steep energy increase Large Distortions Ti 4+ is an electronically soft ion that can easily accommodate the distorted octahedra Mn 4+ cannot accommodate distortions, so Ni 2+ is pushed into the most distorted sites d 0 elements such as Ti 4+, Mo 6+, V 5+, Nb 5+,Zr 4+ easily accommodate distortions and thereby help stabilize disorder A Urban, A Abdellahi, S Dacek, N Artrith, G Ceder, Phys. Rev. Lett. 119, , DOI: /PhysRevLett (2017)

23 Valence constraints is a big problem in cathodes Li-excess cathodes Li 1+x M 1-x O 2 Valence of M é High-valent ion (inactive) Nb 5+, Mo 6+, Ti 4+, Zr 4+, Redox element Ni 2+, Mn 3+, Fe 3+, V 3+ Layered cathodes LiMO 2 -> MO 2 High capacity means high oxidation of M (e.g. Ni 4+ ). Implies safety issues

24 Percolation requirement reduces theoretical capacity from redox metal Li-excess cathodes Li 1+x M 1-x O 2 High-valent ion (inactive) Nb 5+, Mo 6+, Ti 4+, Zr 4+, Valence of M é Redox element Ni 2+, Mn 3+, Fe 3+, V 3+ Li 1.25 Nb 0.25 Mn 0.5 O 2 Li 1.2 Ni 0.32 Ti 0.35 Mo O 2 147mAh/g. 193mAh/g

25 Percolation requirement reduces theoretical capacity from redox metal Li-excess cathodes Li 1+x M 1-x O 2 Valence of M é High-valent ion (inactive) Nb 5+, Mo 6+, Ti 4+, Zr 4+, Redox element Ni 2+, Mn 3+, Fe 3+, V 3+ Li 1.25 Nb 0.25 Mn 0.5 O 2 Li 1.2 Ni 0.32 Ti 0.35 Mo O 2 147mAh/g. Oxygen oxidation Li-O-M 193mAh/g Li-O-Li Li M M O Li Li M three Li-O-M e.g., stoichiometric layered Li-M oxides M bands O bands M M O Li Li Li one Li-O-Li, two Li-O-M e.g., Li-excess layered/cationdisordered Li-M oxides e.g., Li(Li 1/3 M 2/3 )O LiMO 2 2 Li Nature Chem., (2016)

26 High voltage charging leads to oxygen loss Li 1.2 Ni 1/3 Ti 1/3 Mo 2/15 O 2 DEMMS ~4.3 V, ~185 mah/g STEM/EELS shows densification at surface PRISTINE AFTER 20 CYCLES

27 Li diffusion and redox in cation-disordered cathodes are tied to one another Li excess => 0-TM percolation for Li diffusion Limited TM contents (Limited TM redox) Oxygen-redox for High redox capacity Degrades 0-TM percolation by removing Li-excess O-loss with cation densification Too much oxygen oxidation leads to structural instability

28 Li 1+x M 1-x O 2 è Li 1+x M 1-x O 2-y F y : fluorination LN15 Li 1.15 Ni Ti Mo 0.1 O 2 LNF15 Li 1.15 Ni 0.45 Ti 0.3 Mo 0.1 O 1.85 F % metal redox capacity increase XRD a = Å 150~200 nm TEM-EDS O F NMR density = 4.25 kg/l Ni Mo Ti J. Lee, G. Ceder et al, Nat. Comm, 8, art number 981 (2017)

29 Fluorination reduces polarization oxygen loss DEMMS shows less O-loss with fluorination Li 1.2 Ni 1/3 Ti 1/3 Mo 2/15 O 2 ~4.3 V, ~185 mah/g 587Wh/kg Li 1.15 Ni 0.45 Ti 0.3 Mo 0.1 O 1.85 F 0.15 ~4.5 V, ~220 mah/g 790Wh/kg J. Lee, G. Ceder et al, Nat. Comm, 8, art number 981 (2017)

30 Why F/O substitution is possible in disordered materials and NOT in layered oxides } TM-F bonds are very high energy } F incorporation only possible in locally Li-rich environments In layered structure too many TM around oxygen to substitute by F Fluorine tolerates at most one metal bond W. Richards, S. Dacek, D. Kitchaev, G. Ceder. Fluorination of Li-Excess Transition Metal Oxide Cathode Materials. Adv. Energy Mater. (2017)

31 First principles calculated solubility in layered cathodes Minimal solubility in ordered LiNiO 2 (0.38% F at 750C) High solubility in disordered LiNiO 2 LiNiO 2 fraction LiF

32 Universal solubility of LiF in disordered rocksalts 32

33 Advantages of Li-excess disordered rocksalts Reducing the constraint of layeredness enables a large chemistry playing field of Co-free materials. Much more compositional freedom Many materials have > 200mAh/g capacity (unoptimized) and some approach 300mAh/g. Energy densities Wh/kg and likely more. Fluorination gives additional compositional degree of freedom to lower overall cation valence: increase theoretical capacity and increases stability at TOC Unlike in the ordered layered materials, F incorporation is possible due to the local Li-excess environments. Cation disorder is promoted by the presence of d 0 elements: Ti 4+, Zr 4+, Nb 5+, Mo 6+, V 5+ We have a real opportunity to create novel cathode materials based on novel chemistries and true oxygen redox

34 Lawrence Berkeley Laboratory UC Berkeley Thank You